The State of Origin competition is a series of three games of rugby league played every year between New South Wales and Queensland, and is the source of much rivalry. It's related to federation because without federation, there wouldn't be the two states of NSW and QLD.
The Sheffield Shield is an Australian cricket competition between teams from each of the states. It is related to federation because without federation, the states that compete would not exist.
Golf is a sport played all around the world, and there are many interstate competitions around Australia. Without multiple states there would not be interstate competitions, therefore federation is required.